Third-order nonlinear-optical properties of gold natioparticles embedded in Al2O3, ZnO and SiO2 have been investigated by the Z-scan method at the wavelength of 532 nm using nanosecond Nd3+:YAG laser radiation. The nonlinear refractive index, nonlinear absorption coefficient, and the real and imaginary parts of the third-order nonlinear susceptibility are deduced. The results of the investigation of nonlinear refraction using the off-axis Z-scan configuration are presented and the mechanisms responsible for the nonlinear response are discussed. The prevailing influence of the electronic Kerr effect over the possible thermo-optical contribution is demonstrated. (C) 2007 Elsevier B.V. All rights reserved.